1. Field of the Invention:
The device of the present invention generally relates to nuclear fuel assemblies for use in nuclear reactors, and, more particularly, to a new and improved channel spring and stop assembly for a nuclear fuel assembly especially adapted for use in a boiling water reactor (BWR).
2. Description of the Prior Art:
The generation of a large amount of heat energy through nuclear fission in a nuclear reactor is well known. This energy is dissipated as heat in elongated nuclear fuel rods. A plurality of the nuclear fuel rods are grouped together to form separately removable nuclear fuel assemblies. A number of such nuclear fuel assemblies are typically arranged in a matrix to form a nuclear fission reaction. The core is typically submersed in a fluid, such as light water, that serves as a coolant for removing heat from nuclear fuel rods and as a neutron moderator.
A typical nuclear fuel assembly may be formed by a 7.times.7 or an 8.times.8 array of spaced-apart, elongated rods supported between upper and lower tie plates.
Examples of such typical nuclear fuel assemblies are depicted in and described in U.S. Pat. Nos. 3,350,275; 3,466,226 and 3,802,995. In a typical core the matrix of fuel assemblies must be maintained in a fixed spatial relationship. A known technique for maintaining a spacing in the channel between fuel assemblies is disclosed in U.S. Pat. No. Re. 27,173 which employs a spring biasing technique intended to compensate for variations in fuel assembly lengths and widths by mounting spring assemblies on adjacent fuel assemblies so that the springs of adjacent assemblies bias against each other to maintain a separation force. A stop member associated with the springs is utilized to assure minimum separation between fuel assemblies.
A large BWR reactor core typically comprises dozens of fuel assemblies not all of which are removed and replaced during each refueling event. Therefore, the replacement fuel assemblies must be physically and dimensionally compatible with the existing fuel in the core and must not interfere with the channels between fuel assemblies or with the movement of control rods.
Moreover, replacement fuel assemblies must be designed with a channel spring and stop assembly which can maintain a fixed spatial relationship between adjacent fuel assemblies and which has a compatible interface with existing fuel assembly designs.
It is also desirable for replacement fuel assembly to be designed for ease of manufacturing and to afford flexibility in adapting new fuel to existing fuel assemblies.